The overall objective of this work is to elucidate the mechanism by which specific environmental signals stimulate human pheochromocytoma cells in tissue culture to synthesize and secrete vasoactive intestinal peptide (VIP), a neuropeptide that is not present in normal adrenal medulla but occasionally appears as an ectopic hormonal secretion of pheochromocytoma. Hypersecretion of VIP in man causes the "watery/diarrhea hypokalemia, achlorgydria syndrome." Study of the hormonal regulation of gene expression in pheochromocytoma may provide a system by which factors determining ectopic hormone biosynthesis in neuroendocrine tissues in general may be elucidated. In preliminary studies, it was found that pheochromocytomas maintained in culture develop the ability to produce and secrete VIP. Production of VIP in these cells is regulated by nerve growth factor (NGF) and dexamethasone. During the first phase of this project, the optimum conditions for studying VIP production at the molecular level will be established, including determining the time courses and dose response curves for the effects of NGF and dexamethasone and evaluating the influence of serum components on VIP production. A complimentary DNA molecule encoding the precursor of VIP will then be constructed and used to determine whether the culture conditions, NGF, or dexamethasone are acting at a transcriptional or translational level to influence VIP synthesis. Finally, the VIP gene itself will be examined for features associated with active gene expression, allowing comparison of these features in tissues which have the potential to produce VIP given the appropriate environmental signals. (C)